The peculiar pleurocerids of the Interior Highlands II: Pleurocera simplex ozarkensis

There is no substitute for field experience.  You can track the modern scientific literature of malacology with relentless vigilance, pore over the historic monographs, paw through the national collections, dissect those snails, measure ‘em, drag their proteins through a gel or sequence every nucleotide in their genome.  All those data are just pieces in a puzzle scattered across your table top.  They will not fit together until you wade knee-deep into the river and look down at a population of the living organisms in their natural environment.  And again, in the creek upstream.  And again, in the lake downstream.  And repeat, next drainage over.  You cannot know them, until you walk with them.

So, on August 31, 2025, I loaded my pickup and set off on a two-week field trip to the Interior Highlands.  My itinerary was a zigzag path south from Jefferson City through the Missouri Ozarks, west across the top of Arkansas and into eastern Oklahoma.  I then planned to cut a giant S-shaped curve back across central Arkansas to cover the Arkansas and Ouachita drainages in one swell foop.  The weather was lovely, the water was low, I met a lot of nice people along the way [1], and had a wonderful adventure.

Christopher Rogers at the Little Lee River, OK.

And the rivers into which I waded those two weeks were strange unto my eyes.  Quite in contrast with the lotic environments of the southern, eastern, and midwestern United States of my long experience, typical streambeds in the Interior Highlands are composed of white, baseball-sized cobble.  And at low water, such as I found in early September of last year, I often found myself stomping dryshod across 40 yards of cobble to reach a two-inch trickle.

But when the rains come, Heaven help the hindmost!  Way back in the woods through which I had stomped to reach all those dry riverbeds last September was everywhere evidence of the floods of May 2025, tangles of storm-washed brush still wrapped around tree limbs 10 feet above my head.  The lotic environments of the Interior Highlands are, in one word, flashy.  In two words, very flashy.  They are a hybrid of an eastern river, and a western dry wash.

And my goodness, Pleurocera potosiensis populations where omnipresent in every river, stream, and mean little trickle I visited my first few days out, sampling south through the Ozarks.  I was heading toward a cluster of four sites that Russ Minton and his colleagues [2] had sampled for their 2017 study of 16S mtDNA sequence divergence in P. potosiensis, which they designated M6, M7, M8, and M10.

Last month we reviewed Minton’s 2017 study in considerable detail, reproducing his Figure 1 map of study sites across the Ozark Highlands of three states.  At left is an enlargement of the little red dashed-line box I drew at the top of last month’s three-state map.  Minton sequenced a total of nine snails from the four populations inhabiting the little rectangle of the Missouri Ozarks have I extracted here, demonstrating two very different haplotypes, five of the typical haplotype (“X”) and four of a second haplotype (about 8% different) that I called Z.  And the middle 40% of Minton’s big gene tree, highlighting those nine haplotypes, is extracted and reproduced below.

So, coming down from the north, I arrived first at Minton’s M10, Clifty Spring.  And the environment didn’t strike me as any different from typical for an Ozark Highland stream – a wide bed of dry white cobble with a trickle of water running through.  I found the spring itself more like a side-pool, a colder pool of clear water at the edge of the stream bed.  And its snail population no different from that of any other Pleurocera potosiensis I had seen in previous days.  Both of the snails Minton had sequenced from that spring in 2017 demonstrated the X haplotype.

It was at Minton’s site M6, as I came near Damascus, that suddenly there shined ‘round about me a light from heaven, and I fell to the earth, and heard a voice saying unto me, “You ain’t in the Ozarks anymore.”  The little stream running under Missouri Road C at site M6 is called Tick Creek on USGS maps, although in Minton’s paper it is referred to as “Trek Creek.”  It was ice cold, crystal clear, bank-full and stable.  And it was rich, and it was productive!

Detail from Minton et al. [2] Fig. 4

The date was September 4, 2025.  And for four days I had been stomping through dreadfully unproductive streams - 90% plain bare dry rock, and 10% plain bare wet rock.  I found nothing green – no moss, no macrophyte, no algae, not even any visible periphyton.  Indeed, I found very little silt, and almost no mud.  Approximately zero visible organic matter of any sort. After four days of this, I had become numb to it.

And suddenly, in tiny little Tick Creek under tiny little Missouri Road C, I had stumbled upon such a lovely, productive, stable little stream that it transported me spiritually out of the dusty Ozarks and back home to the green, rolling hills of Old Virginny.

And my eyes were opened.  And behold, the pleurocerid snails grazing therein were not Pleurocera potosiensis of the Interior Highlands.  They were Pleurocera simplex of the Southern Appalachians.  The shells were not strikingly different.  They seemed to have somewhat larger body whorls relative to expectation for potosiensis, and were entirely missing that strong peripheral keel one often sees in potosiensis, especially on the juvenile shell.

The most striking feature of the Tick Creek population was the black body color, which one never sees in potosiensis.  Black body is a signal feature of P. simplex populations in smaller eastern streams of my long experience.  Pleurocera simplex populations tend to lose that distinctive body coloration in larger streams, and indeed, the subspecies P. simplex ebenum of Cumberland drainages is typically brown/orange of body.  But if you see black in East Tennessee, it’s simplex.

So, referring back to Minton’s map and gene tree. The genetic contrast between the population of snails inhabiting typical Ozark stream M10 and those inhabiting rich, productive stream M6 was as stark as the environmental difference.  All three of the snails sequenced from Tick Creek M6 [3] demonstrated haplotype Z.

The peculiar pleurocerids of Tick Creek (M6).

Driving further south I next arrived at Minton’s site M7, the Missouri Road T bridge over Little Piney Creek.  And there I found another very typical-looking population of P. potosiensis, inhabiting another very typical-looking Ozarkian stream of bare white cobble, like Site M10.  And just as at Site M10, both of the snails Minton had sequenced from site M7 demonstrated haplotype X.

The confirmation I needed for my hypothesis I found at Minton’s site M8, Mill Creek at the State Recreation Area.  There I discovered a side-spring, marked “flowing well” on USGS topo maps, issuing a gorgeous, productive, ice-cold crystal-clear spring run perhaps 100 m long into Mill Creek.  Standing knee deep in Mill Creek, looking upstream with that "flowing well" spring run to my right, I found a mixture of typical-looking brown-bodied P. potosiensis and black-bodied snails indistinguishable from eastern P. simplex.  And at that site, Minton had sampled two snails, one of which proved to bear haplotype X the other of which proved to bear haplotype Z.

The snails at site M8 clearly do not constitute a single randomly-breeding population, but rather an admixture of two populations demonstrating at least some reproductive isolation.  Those are distinct biological species [4].  One must be Pleurocera potosiensis, and the other must be something else.  My hypothesis is that the brown-bodied pleurocerids in Mill Creek bear haplotype X and are correctly identified as P. potosiensis, and that the black-bodied pleurocerids in the side spring bear haplotype Z and are correctly identified as P. simplex.

Dr. R. Ellsworth Call (1856 – 1917) was born in Brooklyn but spent most of his life in The Heartland, teaching in secondary schools across Illinois, Missouri, Iowa, Kentucky, and Indiana [5].  He is best known to friends of the FWGNA Project for the six-part series of papers he published on the Mollusca of Kansas 1885 – 1887 [6], as well as his 1886 collaboration with Henry Pilsbry to describe the genus Pyrgulopsis [7].

And chief among the many and wondrous contributions R. Ellsworth Call made to American malacology in 1886 was his “Description of a new strepomatid mollusk of the Genus Goniobasis,” published in the Bulletin of the Washburn College Laboratory of Natural History, way out in Topeka [8].  In that paper he described the shell of Goniobasis ozarkensis with a large paragraph of adjectives and adverbs including “globosely elongated, faintly bicarinate, body whorl large, obtusely angulate at the periphery.”  The animal he described as “black above.”  The type locality was “Blue Spring, in the Ozark Mountains, Shannon County, Missouri.”  That’s less than 60 miles south of Minton’s Mill Creek site M8.

Goniobasis ozarkensis Call 1886 [9]

We mentioned last month that Goodrich [10] considered Call’s ozarkensis one of the four subspecies of potosiensis, and as such the nomen was transmitted to the present day by Burch [11].  No, those populations are not a subspecies of potosiensis.  At Minton’s Mill Creek site M8 there is clear evidence of reproductive isolation between a population that matches Call’s 1886 description of ozarkensis and a population of typical P. potosiensis.  Let’s transfer Call’s nomen from subspecific level under potosiensis to subspecific level under simplex: Pleurocera simplex ozarkensis (Call 1886).

As a generality, the shell of Pleurocera potosiensis bears a mid-whorl angulation, much more pronounced in juveniles, typically becoming obsolete in adults.  The shell is usually tan, brown, or golden, sometimes bearing bands of darker color.  The body color is never black.   Populations of P. potosiensis are common in rivers and streams throughout the Interior Highlands.

By contrast, the shell of P. simplex ozarkensis never bears a mid-whorl angulation, although sometimes faint carina are evident.  Both shell and body are darker, sometimes black.  Populations of P. simplex ozarkensis are restricted to richer, more stable springs, streams and rivers of the Interior Highlands with significant groundwater input.

Continuing on my journey with my eyes opened by the Damascus-Road experience of Thursday afternoon, September 4, I was able to recognize nine additional populations of P. simplex ozarkensis in the springs and streams I sampled further south through the Interior Highlands, all the way to Hot Springs, Arkansas [12].  And I found plenty of additional evidence of reproductive isolation.  Indeed, I found another mixed population in the Big Piney River about 30 miles south of Mill Creek M8, where “Boiling Spring” bubbles up right on the river margin, spitting a big population of simplex into a huge population of potosiensis, both populations retaining distinctive features [14].

And ultimately, I arrived in Eastern Oklahoma, to dip my boot toe into Sallisaw Creek, the home of Minton’s population OK, the pleurocerid that had launched my 3,400 mile, 15-day Odyssey.  And there I found the pleurocerid population mixed.  My readership will recall that Minton sequenced three individuals from his population OK, and that all three returned the simplex haplotype Z.  I myself could distinguish both species in Sallisaw Creek, mostly simplex, but a significant fraction of potosiensis.  And I will level with you.  Some of the pleurocerid snails in Sallisaw Creek I could not sort to species, with any degree of certainty.

Pleurocera potosiensis and Pleurocera simplex ozarkensis are effectively a sibling species pair.  Often in my 14 days of wading the creeks and rivers of the Interior Highlands, I reached down and drew back a pleurocerid snail I could not firmly identify one way or the other.  It seems quite likely to me that potosiensis and simplex hybridize.  Heaven knows we’ve amply documented that phenomenon in pleurocerid species more different than this pair [15].

And now, turning a practiced eye back on the ten paratypic shells that R. Ellsworth Call illustrated in his original 1886 description, I think it quite likely that shell #2 and shell #9 are P. potosiensis.  I think the population Call sampled at Blue Spring, Shannon CO, Missouri, may have been mixed [16].

Many independent lines of evidence suggest strongly that Pleurocera simplex, like most of the pleurocerids of Eastern North America, evolved in the Paleozoic Era, with the Appalachian Orogeny.  The hypothesis is inescapable that Pleurocera potosiensis evolved from a population of P. simplex after the Interior Highlands were separated by the Cretaceous embayment.

And were Charles Darwin alive today, I feel sure he would hasten to suggest that natural selection is a very likely cause.  At some point in the last 65 my, some population of P. simplex apparently adapted to a flashy, low-nutrient riverine environment, speciated, and spread downstream throughout the Ozark/Ouachita Highlands, leaving its ancestral P. simplex population, indeed hundreds of ancient P. simplex populations, stuck upstream in the creeks.  Grist for a future post, perhaps?  Stay tuned.

 

Notes:

 

[1] In addition to my friends Randy Sarver and Dave Michelson of the MoDNR, whom I acknowledged last month, special shout-outs here to Christopher Rogers with the Grand River Dam Authority in Tahlequah, Oklahoma, and Kyle Gustafson and his students at Arkansas State University in Jonesboro.

 

[2] Minton, R.L., B.L. McGregor, D.M. Hayes, C. Paight, and K. Inoue (2017) Genetic structuring in the pyramid Elimia, Elimia potosiensis (Gastropoda, Pleuroceridae), with implications for pleurocerid conservation. Zoosystematics and Evolution 93(2) 437-449.

 

[3] Minton uploaded these three identical haplotypes into GenBank as MO6A, MO6B, and MO6C, but they were labeled 6-A, 6-C, and 6-E on his figure 4.  I have retained the A-C-E system here.

 

[4] If the rationale for this statement is not immediately obvious to you, please see:

• What is character phase disequilibrium? [4Jan22]

[5] The biographical details on the life of R. Ellsworth Call are extracted from:

• Johnson, Richard I. (1975) R. Ellsworth Call with a bibliography of his works on mollusks and a catalogue of his taxa.  Occasional Papers on Mollusks (MCZ Harvard) 4 (54): 133 – 144.

[6] There’s a paragraph reviewing Call’s surveys of Kansas in the introduction to the Freshwater Gastropods of the Great Plains [FWGGP].

 

[7] Call R. E. & Pilsbry H. A. (1886). On Pyrgulopsis, a new genus of rissoid mollusk, with description of two new forms. Proceedings Davenport Academy of Natural Sciences 5: 9-14.  For more see:

• The SNHTHICACWB Marstonia 5: scalariformis [4Oct22]

[8] Call, R.E. (1886) Description of a new strepomatid mollusk of the genus Goniobasis.  Bulletin of the Washburn Laboratory of Natural History (Topeka) 1(7): 189 – 190.

 

[9] There is no scale bar on the plate, which almost certainly means that the reproduction was 1:1 in the original.  Call stated that “The average dimensions of the seven largest specimens are, for length 10.77 mm, breadth 6.21 mm.”  You do the math.

 

[10] Goodrich, C. (1939) Pleuroceridae of the Mississippi River basin exclusive of the Ohio River system.  Occasional Papers of the Museum of Zoology, University of Michigan 406: 1 – 4.

 

[11] This is a difficult work to cite.  J. B. Burch's North American Freshwater Snails was published in three different ways.  It was initially commissioned as an identification manual by the US EPA and published by the agency in 1982.  It was also serially published in the journal Walkerana (1980, 1982, 1988) and finally as stand-alone volume in 1989 (Malacological Publications, Hamburg, MI).

 

[12] The population in Crystal Springs, AR, where Minton did his morphometric work [13], is almost certainly P simplex ozarkensis.

 

[13] Minton RL, Lewis EM, Netherland B, Hayes DM (2011) Large differences over small distances: plasticity in the shells of Elimia potosiensis (Gastropoda: Pleuroceridae). International Journal of Biology 3(1): 23 - 32.

 

[14] We used a photo of “Boiling Spring” (Texas County, MO) in the photobar at the top of our brand new “Freshwater Gastropods of Missouri” web resource.  Look at the top of the [FWGMO] front page, if you’re curious.

 

[15] For a review of hybridization in the North American Pleuroceridae, see:

• Widespread hybridization between Pleurocera laqueata and P. troostiana in streams of the Tennessee/Cumberland [15Oct24]
• Reticulate evolution in the North American Pleuroceridae [12Nov24]

[16] And, rats!  Dick Johnson [5] picked shell #2 as the lectotype.  Let’s keep that a secret, just between me and all two of you who read my irritatingly discursive footnotes, okay?

The peculiar pleurocerids of the Interior Highlands I: Pleurocera potosiensis

You all like maps, am I right?  Who among my elite and erudite readership does not, at least occasionally, revel in an old-time paper map, and lament their impending extinction?

 So last summer I was taking a walk down memory lane in Derring Hall, home to both the Biology Department and the Geology Department at my alma mater [1], Virginia Tech (1973 – 1977).  And I stopped to admire a gigantic (1996) Tectonic Map of North America [2], preserved behind floor-to-ceiling Plexiglas sheeting outside the Geology Department office.  And snapped the photo below.

I was stricken by the obvious inference that at some point in the ancient past, a chunk broke off my old familiar East Tennessee stomping grounds and floated west beyond the Mississippi into the wilds of Arkansas and Oklahoma.  That chunk is the Ouachita Mountains.  Indeed, the tectonic theory of North America suggests that the Ouachita Mountains and the Appalachians are “sisters,” created together by the collision of the Gondwanan plates around 300 mya, subsequently separated by the Cretaceous Embayment.

 

Like most of us here in The East, I tend to lump the Ouachita Mountains together in my mind with the Ozark Highlands, but the Ozarks were uplifted as a dome and subsequently dissected.  That rugged region, extending north from NW Arkansas well into Missouri, is not visible in the 1996 map above.  I cannot find any consensus on the date or cause of the Ozark uplift; it may also have been a function of the Paleozoic orogeny that formed Ouachita Mountains, or may have been post-Paleozoic.  That doesn’t matter for the yarn I’m fixin’ to spin.

 

Melania potosiensis [6]

The most important thing is the snails.  Today, the characteristic freshwater gastropod of the USGS Interior Highlands Physiographic Division, which includes the Ozark Highlands, the Ouachita Mountains, and the Arkansas Valley between them, is Pleurocera potosiensis.  That snail is a regional endemic – widespread and locally quite common in rivers and streams throughout the physiographic division, unknown elsewhere.  Shi-Kuei Wu and colleagues [3] documented populations across the entire southern half of Missouri, an observation we have now thoroughly confirmed [FWGMO map].  Christian and Hayes [4] reported P. potosensis populations equally widespread across the northwestern quarter of Arkansas.  The species range also extends westward into Oklahoma, and touches the SE corner of Kansas [FWGGP map].  Further south, populations of P. potosiensis become less common in tributaries of the Arkansas River, and spotty in tributaries of the Ouachita.

Isaac Lea’s brief, Latinate description of Melania potosiensis appeared in 1841 [5], as #46 in that same “litter of 57 pleurocerid puppies” I catalogued in my essay of [20Aug25], with a more complete English description and figure following in 1843 [6].  Tryon [7] transferred the nomen to Goniobasis, reprinting Lea’s 1843 description verbatim, while adding, perceptively, 

“Were it not for the wide differences of locality I should suspect this to be identical with simplex.  I have not seen specimens, but the figure and description are certainly very close to that species.”

Goodrich [8] recognized four subspecies.  The most widespread he identified as Goniobasis potosiensis plebius (Anthony 1850), which he considered common in rivers and creeks throughout the Ozarkian area of Missouri, Arkansas, and Eastern Oklahoma.  The typical subspecies Goniobasis potosiensis (ss) he considered “a shell of the upland streams of a few Missouri counties” only.  Goodrich also recognized a Goniobasis potosiensis crandalli (Pilsbry 1890) “known only from Mammoth Springs, Fulton County, Arkansas” and a Goniobasis potosiensis ozarkensis (Call 1886) which he considered a “depauperate” form [9, 10], “only from springs of Shannon, Carter, Washington, Dent, and Camden counties, Missouri.”  Burch [11] transmitted Goodrich’s entire four-subspecies system along with their ranges verbatim, pausing only to swap out the well-established genus Goniobasis for the zombie taxon [12] Elimia.

 

As a laboratory for the study of evolution, the widely-dispersed and genetically diverse Ozark/Ouachita populations of P. potosiensis may rival the Pleurocera proxima populations of the southern Appalachians [14].  By the Grace of God, they seem to have slipped through 200 years of malacological malpractice to arrive in the 21st century almost unsplit by taxonomic exuberance.  Our colleague Russ Minton and his coworkers took advantage of this happy situation in both a shell morphological study [15] published in 2011, and in a 2017 study of intraspecific genetic divergence [16].

 

The 2011 paper, a landmark-based study of 500 individual shells sampled at 25 m intervals from a spring run and adjacent tributary of the Ouachita River in Garland County, Arkansas, was most memorable for its peculiar Figure 1.  True to the school of landmark-based morphometrics, there was no scale on Minton’s photo, reproduced below.  The caption simply read, “Morphological variation in Elimia potosiensis from Arkansas.”

Minton et al. [15] Figure 1

The first thing that struck me when I read Minton's 2011 paper some years ago was that the second shell (B) was clearly that of Leptoxis arkansensis, not P. potosiensis at all.  I’m sure that’s a common mistake, to naïve eyes.  I myself had no field experience in The Interior Highlands until 2024.  All I knew about the malacofauna of that biogeographically fascinating part of the world until quite recently was what I had learned from a week studying the Wu-Oesch-Gordon Missouri collections at the University of Colorado Museum in 2021, and even there I found some not-insubstantial Leptoxis/Pleurocera confusion.

But what really struck me upon my first reading of Minton’s 2011 morphometric study was that third shell (C).  It was clearly out of scale with the other two – probably 30% magnified, by my eye.  And recalling the words of Tryon, I found that shell completely indistinguishable from my old friend from the East, Pleurocera simplex. 

 

I picked up my first Pleurocera simplex when I was a student at Virginia Tech back in 1975, and since then have sampled hundreds of populations from SW Virginia all across Tennessee, Kentucky, and north Alabama.  I have published five papers and notes on P. simplex thus far [17], supplemented by at least eight blog posts.  Rob Dillon knows Pleurocera simplex.  Were populations of P. simplex on that plate-tectonic raft when it broke loose from its Tennessee moorings and washed up on the banks of the Wide Missouri way back in the Paleozoic?

 

Russ Minton’s 2017 paper was an even more interesting read.  He and his colleagues reported the results of two separate studies, a fine-scale study using ISSR markers very similar to the allozyme study I published on P. proxima way back in 1988 [14], and a study of 16S sequence divergence at the scale of many of the allozyme studies I published on P. proxima and others in the early-2000s [18].  The fine-scale study was poorly designed, with only 10 snails sampled for each of 12 sites down approximately 500 meters of stream, such that the ISSR markers (110 unique genotypes among the 120 individuals) returned no results.  But the study of mtDNA sequence divergence was fascinating.

Adapted from Figure 1 of Minton et al [16]

Minton and colleagues sequenced the 16S gene from 61 individual snails identified as “Elimia potosiensis” from 16 sites in southern Missouri, 14 sites in northern Arkansas, and 1 site in eastern Oklahoma.  Their map of sample sites, color-coded by drainage system, is reproduced above. This is the second-best data set [19] on interpopulation mtDNA sequence divergence ever published for any nominal species of pleurocerid snail.

 

Minton discovered four strikingly different sets of sequences, each about 10% different from the other three, none of which demonstrated any correlation to geography whatsoever.  Minton’s Figure 4 is reproduced below.  I have labelled those four sets of haplotypes X, Y, Z, and L.

 

Who among my loyal readership finds this result surprising, in the least?  How many blog posts have I dedicated to the phenomenon of mitochondrial superheterogeneity in freshwater gastropods [20], since Bob Frankis and I first stumbled upon the phenomenon [21] back in 2004?  Speaking now to any new visitors we might be entertaining in the columns of the FWGNA Blog this month, and to any other readers who might otherwise imagine that double-digit mitochondrial sequence diversity is unusual within pleurocerid populations, you are earnestly invited to footnote [22] for approximately 30 minutes of remedial study. 

Adapted from
Minton [16] Fig. 4

Ah, but.  Some of the details in Minton’s Figure 4 did not match the expectation I have developed over years of familiarity with mtSH.  Yes, Minton identified a majority haplotype, which I have labelled X, just as Whelan and Strong found in the best study of mtSH to date, their 2016 paper on Alabama Leptoxis [19].  Whelan & Strong also discovered five other haplotypes, all demonstrating double-digit sequence divergence from the majority haplotype, four of which were quite rare.  My jetlagged wildebison model would suggest that those five rare Leptoxis haplotypes had evolved somewhere far away (in snail-space or snail-time) to be scattered into the present-day study area by dirty birds.  And in the case of the Whelan & Strong dataset, we cannot identify four of those other five places.  Fine.

And yes in fact, the cluster I have labelled Y in Minton’s Figure 4 does fit our expectation for mtSH, under the jetlagged wildebison model.  That haplotype is 10.1% different from haplotype X, it is rare, and there is no divergence among the five individuals (found in three populations) carrying it.

 

But the clusters labelled Z and L in Minton’s Figure 4 do not look like mitochondrial superheterogeneity to me.  They are not rare.  Moreover, both show evolutionary structure – a branching within cluster.  Within cluster Z, for example, Population #2 branches first – the only two individuals sampled for the study, together.  Then population OK (from Oklahoma) branches off – all three of the individuals sampled, together.

 

And as I sat at my desk late one evening several years ago, examining the population OK data published in that paper, a bell tinkled way in the back of my addled brain.

 

Russ Minton only figured one shell in his 2017 paper, pasted into the corner of his Figure 2, showing a map of the sample sites for his ISSR study.  Quoting his Figure 2 caption: “Shell of E. potosiensis from population OK is shown.”  I have clipped that shell from Russ’ 2017 Figure 2 and pasted it in the lower left corner of my adaptation of his Figure 1 map above.  That is very clearly the same scaleless individual shell he labelled “Elimia potosiensis from Arkansas” in his 2011 paper.  And that shell looked as much like Pleurocera simplex in 2017 as it did in 2011.

 

All three of the individual snails that Minton sequenced from Oklahoma carried haplotype Z.  And the other 13 individuals carrying haplotype Z were scattered all across Minton’s three-state study area, as I have marked in red above.  In what direction could all those clues be leading?  Tune in next time.

 

Notes:

 

[1] For sweet, gauzy memories from my halcyon days at dear old Virginia Tech, see:

• Water hardness, stream size, and A.E. Boycott: A New River Reminiscence. [8July25]

[2] Muehlberger, W.R. (1996) Tectonic Map of North America.  American Association of Petroleum Geologists, Tulsa, OK.

 

[3] Wu, S-K., Oesch, R. & Gordon, M. (1997) Missouri Aquatic Snails. Jefferson City: Missouri Department of Conservation. 97 pp.

 

[4] Christian, A. D. and D. M. Hayes (2007) Diversity and distribution of freshwater gastropods from the Ozark Region of Arkansas.  Arkansas Game & Fish Commission, unpublished report. 34 pp.

 

[5] Lea, Isaac (1841) Continuation of Mr. Lea's paper on New Fresh Water and Land Shells.  Proceedings of the American Philosophical Society 2: 11 – 15.

 

[6] Lea, Isaac (1843) Description of New Fresh Water and Land Shells.  Transactions of the American Philosophical Society (New Series) 8: 163 – 250.

 

[7] Tryon, G. W. (1873) Land and Freshwater shells of North America Part IV, Strepomatidae.  Smithsonian Miscellaneous Collections 253: 1 - 435.

 

[8] Goodrich, C. (1939) Pleuroceridae of the Mississippi River basin exclusive of the Ohio River system.  Occasional Papers of the Museum of Zoology, University of Michigan 406: 1 – 4.

 

[9] We first mentioned “depauperization” in our essay of [20Aug25] on Melania acutocarinata.  Goodrich [10] defined “depauperization” as “the outward manifestation of disease, accident or malnutrition or a reaction to inimical environment.”

 

[10] Goodrich, Calvin (1939) Aspects of depauperization.  The Nautilus 52: 124 – 128.

 

[11] This is a difficult work to cite.  J. B. Burch's North American Freshwater Snails was published in three different ways.  It was initially commissioned as an identification manual by the US EPA and published by the agency in 1982.  It was also serially published in the journal Walkerana (1980, 1982, 1988) and finally as stand-alone volume in 1989 (Malacological Publications, Hamburg, MI).

 

[12] We reviewed the taxonomic controversy here:

• Goniobasis and Elimia [28Sept04]

It ultimately didn’t matter, because both Goniobasis and Elimia were synonymized under Pleurocera by Dillon [13] in 2011.

 

[13] Dillon, R. T., Jr. (2011) Robust shell phenotype is a local response to stream size in the genus Pleurocera (Rafinesque, 1818). Malacologia 53: 265-277. [pdf]  For a review, see:

• Goodbye Goniobasis, Farewell Elimia [23Mar11]

[14] General references on the population genetics of P. proxima:

Dillon, R.T. and G.M. Davis (1980) The Goniobasis of southern Virginia and northwestern North Carolina: Genetic and shell morphometric relationships. Malacologia 20: 83-98. [pdf]

Dillon, R.T. (1984) Geographic distance, environmental difference, and divergence between isolated populations. Systematic Zoology 33:69-82. [pdf]

Dillon, R.T. (1988) Evolution from transplants between genetically distinct populations of freshwater snails. Genetica 76: 111-119. [pdf]

Dillon, R.T. (1988) The influence of minor human disturbance on biochemical variation in a population of freshwater snails. Biological Conservation 43: 137-144. [pdf] For a review, see:

• Intrapopulation gene flow: The polymorphic Pleurocera of Naked Creek [12Oct21]

[15] Minton R.L., Lewis E.M., Netherland B, Hayes D.M. (2011) Large differences over small distances: plasticity in the shells of Elimia potosiensis (Gastropoda: Pleuroceridae). International Journal of Biology 3(1): 23 - 32.

 

[16] Minton, R.L., B.L. McGregor, D.M. Hayes, C. Paight, and K. Inoue (2017) Genetic structuring in the pyramid Elimia, Elimia potosiensis (Gastropoda, Pleuroceridae), with implications for pleurocerid conservation. Zoosystematics and Evolution 93(2) 437-449.

 

[17] General references on the population genetics of P. simplex in the Southern Appalachians:

Dillon, R. T., Jr., & G. M. Davis (1980) The Goniobasis of southern Virginia and northwestern North Carolina: Genetic and shell morphometric relationships. Malacologia 20: 83-98. [pdf]

Dillon, R. T., Jr., & J. D. Robinson (2007) The Goniobasis ("Elimia") of southwest Virginia, I. Population genetic survey. Report to the Virginia Division of Game & Inland Fisheries, 25 pp. [pdf]

Dillon, R. T., Jr. (2016a) Two reproductively isolated populations cryptic under Pleurocera simplex (Say, 1825) inhabiting Pistol Creek in Maryville, Tennessee. Ellipsaria 18(2): 15-16. [pdf]

Dillon, R. T., Jr. & J. D. Robinson (2016) The identity of the "fat simplex" population inhabiting Pistol Creek in Maryville, Tennessee. Ellipsaria 18(2): 16-18. [pdf]

Dillon, R. T., Jr. (2016) Match of Pleurocera gabbiana (Lea, 1862) to populations cryptic under P. simplex (Say, 1825) Ellipsaria 18(3): 10 - 12. [pdf]

 

[18] Regional surveys of pleurocerid population genetics:

Dillon, R. T. and A. J. Reed (2002) A survey of genetic variation at allozyme loci among Goniobasis populations inhabiting Atlantic drainages of the Carolinas.  Malacologia 44: 23-31. [pdf]

Dillon, R T. and J. D. Robinson (2009) The snails the dinosaurs saw: Are the pleurocerid populations of the Older Appalachians a relict of the Paleozoic Era?  Journal of the North American Benthological Society 28: 1 - 11.  (Rosemary Mackay Award)  [pdf]

Dillon, R. T. and J. D. Robinson (2011) The opposite of speciation: Population genetics of Pleurocera (Gastropoda: Pleuroceridae) in central Georgia.  American Malacological Bulletin  29: 159-168.  [pdf]

 

[19] The blue ribbon goes to the data set of Whelan, N.V. & E. E. Strong (2016) Morphology, molecules and taxonomy: extreme incongruence in pleurocerids (Gastropoda, Cerithiodea, Pleuroceridae). Zoologica Scripta 45: 62 – 87.

 

[20] A search on the word “superheterogeneity” using the box in the upper right of your screen will return hits in an impressive 24 essays.  And that doesn’t even include the essays I posted on the subject before I coined the term “mitochondrial superheterogeneity” in 2016.

 

[21] Dillon, R. T., and R. C. Frankis. (2004) High levels of DNA sequence divergence in isolated populations of the freshwater snail, Goniobasis.  American Malacological Bulletin 19: 69 - 77. [pdf]

 

[22] Mitochondrial superheterogeneity (mtSH), where two or more of the members of a single population demonstrate greater than 10% divergence in any single-copy mtDNA gene, not sex linked, is remarkably common in freshwater gastropods.  In pulmonate populations, I wouldn’t be surprised if most or all mtSH is ultimately traceable to cytoplasmic male sterility [23].  In prosobranch populations, however, I think mtSH is a signature of great age, plus low-frequency long distance dispersal, the “Jetlagged Wildebison Model.”  Here is a sample of my previous posts on mtSH:

• The Snails the Dinosaurs Saw [16Mar09]
• Mitochondrial superheterogeneity: What we know [15Mar16]
• Mitochondrial superheterogeneity: What it means [6Apr16]
• Mitochondrial superheterogeneity and speciation [3May16]
• Mitochondrial heterogeneity in Marstonia lustrica [3Aug20]
• Testing the periwinkle hypothesis [9May23]

[23] David, Patrice, Cyril Degletagne, Nathanaëlle Saclier, Aurel Jennan, Philippe Jarne, Sandrine Plénet, Lara Konecny, Clémentine François, Laurent Guéguen, Noéline Garcia, Tristan Lefébure, Emilien Luquet (2022) Extreme mitochondrial DNA divergence underlies genetic conflict over sex determination.  Current Biology 32: 2325 - 2333.  https://doi.org/10.1016/j.cub.2022.04.014.  For a review, see:

• Cytoplasmic Male Sterility in Physa! [9June22]

Art, science, and public policy: A dialogue in three languages

I have a lot of friends and family who enjoy travel, and spend a substantial amount of time and money doing it, and imagine that their hobby returns some sort of profit to the intellect or character.  Isn’t travel broadening?  Don’t we learn from exposure to new lands, new cultures, new value systems, new ways of looking at the world?  Yes, of course.  But I found countless worldviews, cultures, and value systems trumpeted in the newspaper at the end of my driveway this morning, ripe for engagement in the aisles of the grocery store across the street this afternoon.  No further travel is required.

As my loyal readership will attest, I have long been fascinated by the diversity of worldviews I encounter in my workday life, and the relationships between them.  The index item at the right of your screen labeled “Worldview Collision” will link to eight essays on the subject when I push the “submit” button on the present post.

The majority of my seven previous essays have explored the relationship between the worldview of science and the worldview of law or public policy, among the most common of the culture clashes in my experience. To understand their proper relationship I have adapted an analogy I first developed about twenty years ago during the height of the most recent creation/evolution controversy between science and religious faith.  Scientists play baseball, lawmakers and regulatory agencies play banjo.  Those worldviews are not incompatible, in the sense that my father was both a banjo picker and a catcher on his high school baseball team.  But not compatible, either.  Nobody ever tries to integrate one with the other. 

I favor the baseball/banjo analogy because most of my colleagues in the world of science seem to have a better grasp on the proper relationship between sports and art than between science and anything else, possibly because we are more objective in the former situation.  We don’t write grant proposals to shortstops, nor debate fiddlers over the 10th grade biology curriculum.

 

Nor collaborate with artists [1].  Thus, an email I received this past August (18Aug25) from one Ms. Julia Galloway [2] fell upon my eye as dew drops from heaven.  She introduced herself as: 

“… a professor and ceramic artist based in Montana. I’m currently working on a project focused on raising awareness about endangered species. For this project, I am creating ceramic urns to represent each threatened, endangered, recovered, and extinct species in the U.S. The project will culminate in the creation of approximately 1,200 urns, with completion expected by 2027.”

Ms. Galloway went on to explain that she had created “400+” urns as of that mid-August date and had (apparently) worked down from the California Condors to the freshwater gastropods, finding her supple hands now poised over a throw of clay to be entitled, “Anthony’s Riversnail.”  And googling about the internet for inspiration, she had found my “fabulous photo” posted on the FWGNA site.  And requested permission to use.

 

How fascinating!  The concept of “endangerment” is purely a matter of law, of course, and “raising awareness” a political objective.  Here an artist addresses a scientist over a matter of public policy. A conjunction of three worlds.

 

On 21Aug25 I replied to Ms. Galloway certifying, as I always do, that all of the images on the FWGNA site are freely available for anybody to use for any purpose whatsoever, and offering to help her in any other way I could.  And I concluded, doing my best to address her in her native tongue: 

“Notice that there's a photo of Leptoxis crassa (“Anthony’s Riversnail”) in situ at the bottom of (the species) page [here].  Which brings me to my final point.  Bless your heart!  These things are brown bumps on a rock.  God made them by throwing little balls of clay at dirt.  If you can make art out of Leptoxis crassa, my cap's off to you.”

 And to the bottom of my email of 21Aug25 I added, “PS – 1,200 urns? Are you nuts?”

Brown bumps in Limestone Creek, AL.

Here the challenge of communication across cultures was on full display.  At no point in her initial email to me, nor indeed in any of her subsequent correspondence, did Ms. Galloway mention the rich symbolism just below the surface of her artwork.  Her urns are modeled after the funerary urns of ancient Egypt.  But, quoting from her website, “displayed empty as a sign of hope.”  Anthony’s Riversnail may be gasping for breath, by this metaphor, but it ain’t dead yet.

 

Ms. Galloway replied immediately thanking me for my “delightful and thoughtful reply,” confessed that she does feel a little bit nuts at times, and asked me if I would like to see images of the urn upon completion. And I responded immediately in the affirmative, and suggesting that she just “throw a couple balls of clay at a flowerpot” to expedite the process.

 

I was tremendously impressed to receive the set of three jpegs below on the afternoon of 22Aug25, less than 24 hours after I had granted Ms. Galloway permission to use FWGNA imagery.  Maybe I shouldn’t have been so surprised – with 400 urns down and 800 to go, she must be nothing if not efficient.  Three individual snails were depicted various faces of the Anthony’s Riversnail urn, one snail crawling to the left (a) and two crawling to the right (b, c), as from the vantage point of a wary stonefly.  None of these images was modeled, as far as I could tell, from anything on the FWGNA site.  At least overtly.

 

Although starkly beautiful in their execution, I immediately noticed a couple significant technical problems with the imagery.  Or at least, they seemed significant to me.  So on 23Aug25 I addressed my third email to Ms. Galloway.

And this time, I felt compelled to speak a little bit of science.  I began with some background on gastropod coiling, so as to introduce the adjectives “sinistral and dextral,” and noted that no case of sinistrality has ever been documented in the Pleuroceridae, as far as I know.  I then wrote:

“You have depicted three individual snails on your urn, am I correct?  The images of which you labeled on the jpegs you sent me yesterday afternoon AO22-a, AO22-b, and AO22-c, yes?  Snail (b) is bearing a dextral shell, correct as you have sculpted.  But snail (a) and snail (c) are bearing sinistral shells.  Not only is that uncomfortable to my eyes, it is unscientific.”

That seemed harsh.  So I added, to soften the blow:

“Perhaps you were working from (somebody else's) closeup photograph of a pleurocerid animal, reversed in some popular publication or on the internet?   Amateurs often publish reversed images, careless of the difference.  In fact, it seems highly unlikely to me that anybody other than a professional malacologist would ever notice the chirality of the snails you have sculpted on your urn.  So if you want to let it go (as Queen Elsa would suggest) I would certainly understand.”

Well, a couple weeks passed.  And I honestly did not think I would ever hear from Ms. Galloway again.  At the rate of one urn per 24 hours, I imagined that she must be well into the unionid mussels by that point, gastropods let go, gone, and forgotten.  But on 2Sept25, I was most pleased to receive yet another lovely communication from my artist-pen-pal:

“Thank you so much for bringing chirality to my attention! I loved reading your email and learning more about gastropods. It's always a treat when I get to hear someone talk passionately about their field of study (especially when they're brown bumps on a rock).

 

Sometimes species have very few images, which was the case with this species. Not knowing about chirality, I flipped some of the images to give myself more viewing angles and compositional options. Now that I know about how snail shells grow, I would like to remake the urn. Would you happen to have any additional images of Anthony's River Snail that you could share?

 

Thank you again for taking the time to share this information with me and for your support! Take care and I hope to hear from you again soon!”

Well no, I myself did not have any additional photos of L. crassa showing anything that the couple images already posted on the FWGNA species page did not.  But on a whim, I executed simple a google-image search on “Athearnia anthonyi” and landed, of course, on the Wikipedia page [3].  And good grief.  The image at the top of the Wikipedia page is sinistral!

Wikipedia. From Dick Biggins, USFWS.

So on the evening of 4Sept25 I addressed my fourth email message to Ms. Galloway, apologizing on behalf of the entire profession of freshwater malacology, re-assuring her that Dick Biggins (the donor of the photo) is a careful worker and confessing that I could not imagine that he himself would upload a mirror-reversed image.  But regardless of how the error occurred, I was sorry that some member of our extended community had not fixed it by now.  Not it.

 

I then suggested three remedies: (1) Sculpt the Wikipedia image from a mirror, (2) Adjust the Wikipedia image using the Photoshop mirror-image-reverse button, or (3) model from some other pleurocerid. Honestly, at the resolution of a funerary urn, all pleurocerid bodies are indistinguishable.  I sent her a good image of some other pleurocerid individual crawling to the viewer’s right, so that she would have both left-travelling dextral and right-travelling dextral models to work from.

 

And on 7Sept25 Ms. Galloway thanked me once again, and asked me if I would like to see images of “the new and improved urn when it is completed?”  To which I replied in the affirmative.  But I never heard from her again.  And that’s OK.

 

The philosopher Ian Barbour (1923 – 2013) has suggested [4] that there are four ways in which worldviews might relate: (1) independence, (2) dialogue, (3) conflict and (4) compatibility.  Independence is the unexamined status quo, compatibility a pipe dream, and conflict is right out.  I love, love, love dialogue.

 

The relationship I have demonstrated above is (2) a dialogue between the worldview of science and the worldview of art.  One might subclassify it as (2a) science helps art.  Ms. Galloway asked me to help her.  I did everything I could to do so.

 

Science and art are not incompatible, here obviously.  But mark me well.  Science and art are not compatible either.  They are very simply, and very profoundly, different.  Ms. Galloway is an artist, and she took the lead in this interaction, and I (a scientist) did what I could to help her create a work of art, and at no point did anything that happened between us during our entire two-week interaction have anything to do with science whatsoever.  The pleurocerid images she carved into that pot could bear sinistral shells, or dextral shells, or polka-dot shells, it does not matter.  And in fact, she never asked me for any of the free advice I offered her at any point, and in retrospect, I may have been interfering with the creative process, and if I ever hear from her again, I will apologize for butting in.

 

But I can’t help it, I love that sort of thing. The proper relationship between our worldviews is one of dialogue.  A dialogue with a fine artist is like an expedition into the bush with a Hottentot, from the seat of my own kitchen table.

 

And here is the most interesting thing about my two-week dialogue with Ms. Galloway.  This particular artist’s motivation was not artistic, but political. 

 

The Oxford Dictionary defines art as “an expression of human skill producing works to be appreciated primarily for their beauty or emotional power.”  But to quote from Ms. Galloway’s website, she considers her work “a catalyst for social change.” 

 

She selected Anthony’s Riversnail as one of her 1,200 subjects because that particular gastropod was entered onto the Federal Endangered Species list on April 15, 1994, see 59 FR 17994-17998 [5]. And “By creating an urn for each (such) species, (she) is making (rarely-seen) species visible, and through this awareness, compassionate action is possible.”  In other words, Ms. Galloway apparently thinks that the worldview of art and the worldview of politics are compatible, such that the former can influence the latter.

 

Bless her heart.  You will have by now noticed that no representative from the world of politics or public policy walked into the bar with the artist and the scientist to this point in my essay, nor will one subsequently appear.  I myself was awarded a AAAS Congressional fellowship many years ago, and learned just enough of the language spoken on Capitol Hill 1981 – 82 to appreciate my limitations.  And I do know quite a few hardworking biologists employed by natural resource agencies, both state and federal. And speaking now for all the legislative bodies and all the regulatory agencies and all the departments of natural resource management involved in all the endangered species conservation nationwide, as well as the entire [6] gastropod fauna of Limestone Creek, Madison County, Alabama, thanks for the pot.  Not a great likeness, but it’s lovely, dear, it really is.

Dave Michaelson & Randy Sarver

Art and Public Policy have different languages, different cultures, different values, and different ways of looking at the world. That they are not incompatible is witnessed by Ms. Galloway herself, who is both an artist and a social activist.  But the worldviews are not compatible, either.  Neither art nor public policy can affect the other, any more than the marching band affects the halftime score, or the halftime score the marching band.

 

But lest we condescend.  Of all the holders of all the worldviews of all the world – Art, Science, Business, Finance, Law, Medicine, Engineering, Religious Faith, Harry Potter, or Star Trek, we scientists are the most arrogant.  The notion of science-based public policy is just as absurd as pottery-based public policy, and none of us seems to realize it.

 

On the morning of 4Sept25, the same day I was to send my fourth email to Ms. Galloway, I met my good friend Randy Sarver in the parking lot of the Missouri Department of Natural Resources, Jefferson City. Randy is an excellent biologist, and we have developed a warm relationship over many years, and he helped me unload four flats of empty black-capped vials that used to hold macrobenthic samples collected by the MoDNR 2015 - 2017, and swap them for a fresh batch of MoDNR macrobenthic samples 2017 - 2018. 

 

I am sure that Randy and Dave Michaelson and all our friends at the MoDNR do a great job monitoring the water quality of the Show-Me State, and I would never dream of offering them any advice whatsoever, because I can’t, any more than they would dream of offering me any advice about malacology, because they can’t.  Randy and I are in dialogue.  That’s the thing I love.

 

Notes:

 

[1] I actually did post one previous essay on the relationship between science and art, way back in 2011:

• When Science and Art Collide [4Feb11]

 [2] Learn more about Ms. Galloway from her lavish web presence:

• Julia Galloway [home]
• Endangered Species Project [direct]
• Wikipedia [page]

 [3] Wikipedia, accessed 10Dec25 [link]

 

[4] Here I am generalizing Barbour’s thought on the science – religion relationship to the relationship between worldviews of any sort.  His “fourfold typology” was most clearly stated in:

• Barbour, I. G. (2000) When Science Meets Religion: Enemies, Strangers, or Partners?  Harper, 205 pp.

[5] For the Democrats among my readership, who imagine that findings such as those published in the Federal Register on 15Apr94 have anything to do with science whatsoever, please refresh your memory with the ten essays I have written on the Snake River Physa scandal to date.  Actually, you could skip the first six, if you want, and go straight to:

• The SRALP and the SRNLP: A new hope [14May24]
• The SRALP and the SRNLP: Physa acuta were found [11June24]
• The Twelve Phascinating Physa of Bliss [2July24]
• Cytoplasmic Male Sterility in the Snake River Physa [7Aug24]

[6] Fourteen species comprise the exuberant gastropod fauna of Limestone Creek: four pleurocerids, three hydrobioids [7], three viviparids, and four pulmonates.  I feel certain that all have benefited from the endangered status of their most-famous member.

[7] Counted among the Limestone Creek hydrobioids is a population of Marstonia olivacea, which is a senior synonym of Marstonia ogmorhaphe, which was the other gastropod entered onto the Federal Endangered Species list 15Apr94.  And hence that hydrobiid population should be every bit as federally-protected as the pleurocerid "Athearnia anthonyi," but it isn't, because public policy has absolutely nothing to do with science.  For more, see:

• Is Marstonia olivacea extinct? [19Sept23]